Power
and Precision is a stand-alone statistical power analysis software package that is
used for the calculation of a sample size for a planned study.
The program features an unusually clear interface, and many tools
to assist the user in developing an understanding of power analysis.
It incorporates the ability to create tables, graphs, and reports
with a single click.

Because with this program:

The interface is a pleasure.

The report is both detailed and clear.

The table and graphs are created effortlessly, and they get it
exactly right.